Inability to Fulfil a Vow

As-salaamu-alaykum

I have learnt that when a person commits a sin, he should immediately make sincere taubah and follow it up with a good deed. I was involved in a detrimental sin some time back. In order to stop committing this sin, I made the following vow:

“Every time I commit this sin, to make up for it (to make amends) I vow to Allaah to keep one fast and pay a fixed amount of charity.” (I did it verbally, but this was more or less the wording.)

The constraints of the vow had the desired effect, and for some time I stayed away from the sin altogether. However, after some time, I fell victim to the ploys of Nafs and Shaytaan once again. Each time I committed the sin, I made taubah, and then fulfilled the conditions of my vow as soon as I could. However, these conditions are taking a physical and an even heavier financial toll on me.

My question is: (1) Is there any other easier method for me to fulfill this vow as I don’t want to break it?
(2) If not, is there any Shar’i method for me to ‘break’ this vow simply because of the physical and (more especially) financial strain it is causing?

Kindly advise, any suggestions will be helpful.

Keep up the good work, May Allaah continue to bless you, guide you and assist you, Ameen.

Please remember us sinful ones in your pious Du’aas.

Jazaak Allah.